The Wi-Fi™ standard describes a number of different types of management frames. One type is a beacon frame which is used to announce the existence of a network. Beacon frames are transmitted at regular intervals to allow Wi-Fi™ stations to find and identify a network. Beacon frames include a timing synchronization function (TSF) time stamp which is used by receiving wireless stations (STAs) to update a local free running clock.
There are many reasons why time synchronization between Wi-Fi™ stations, or more particularly, synchronization between their local clocks, is important. For example where the Wi-Fi™ network is being used to stream media (e.g. audio or video data) the clocks are used to control play back of the received media. If the local clocks in each of a pair of loudspeakers playing the same music track (e.g. in a multi-room music system) are not synchronized (where each speaker is a separate Wi-Fi™ station), the audio from each speaker will not be synchronized and as the clocks diverge (as one runs faster than the other), this will become audible to a listener. Where the pair of loudspeakers operates as a stereo pair, with one playing a left channel of an audio signal and the other playing a right channel of the same audio signal, the two must be even more accurately synchronized or this will be apparent to a listener and affect their listening experience.
The embodiments described below are not limited to implementations which solve any or all of the disadvantages of known methods of synchronizing Wi-Fi™ stations.